Recently, as importance of environment has increased, regulation of carbon dioxide in the air has become strict significantly in domestic and foreign countries. Particularly, since the Kyoto Protocol comes into effect, there has been a worldwide tendency to make an effort to reduce the generation of carbon dioxide which has the longest air retention time, the highest contribution to the greenhouse effect and the largest total emission in Korea and to treat the generated carbon dioxide. Thus, there is a need for an active response to such regulation for the purpose of survival of various domestic industries.
First of all, reduction of carbon dioxide, a typical greenhouse gas (particularly in power plants), is imminent. It is thought that the only technology responding to greenhouse gas to reduce directly the amount of carbon dioxide emitted continuously in the energy-related field is Carbon Dioxide Capture and Sequestration (CCS). However, it seems that interest and investment into CCS technology responding greenhouse gas are very low all over the world, except the leading countries of advanced technology. Therefore, it is required that global interest is given to CCS and active efforts are provided to technological commercialization of CCS to reduce continuous emission of carbon dioxide significantly.
Meanwhile, CCS is the abbreviation of Carbon Capture & Sequestration or Storage and referred to as a series of methods for capturing carbon dioxide produced by human industrial activities from its source before its emission into the air and storing it deeply into the underground or converting it into the other chemicals.
CCS includes capturing, transport, storage and conversion. To apply CCS in a broad range, it is essential to reduce the cost required for capturing that occupies about ⅔ of the total CCS cost. Workplaces requiring CCS include thermoelectric power plants, steel works or cement plants generating a large amount of carbon dioxide. Among those, the highest carbon dioxide emission source is thermoelectric power plants occupying 30% of the total emission of carbon dioxide.
Methods for capturing carbon dioxide generated from thermoelectric power plants may be divided broadly into pre-combustion capturing, post-combustion capturing, and mid-combustion capturing (oxyfuel combustion, chemical looping combustion).
Dry carbon dioxide capturing technology uses a solid absorbent capable of absorbing carbon dioxide to absorb carbon dioxide at an absorption tower, and sends the absorbent to which carbon dioxide is absorbed to a regeneration tower so that the absorbed carbon dioxide may be regenerated and concentrated. Herein, the absorption tower and regeneration tower use a fluidized bed. The absorbent for carbon dioxide discharges energy upon the absorption of carbon dioxide and absorbs energy upon the regeneration of carbon dioxide. Therefore, during the absorption of carbon dioxide, the absorbent should be cooled to prevent degradation of absorption efficiency caused by an increase in temperature of the absorbent. In addition, during the regeneration of the absorbed carbon dioxide, a great amount of energy is consumed to supply the carbon dioxide regeneration heat, and thus reduction of the regeneration heat is the most important problem to be solved for propagation of CCS. As an ideal absorbent for carbon dioxide is a material having low carbon dioxide absorption heat while showing high carbon dioxide absorptivity.
As currently developed technology, post-combustion capturing technology that includes capturing carbon dioxide contained in exhaust gas after combustion is regarded as the easiest technology applicable to the existing sources generating carbon dioxide. This is a method for separating and recovering carbon dioxide by adsorbing/desorbing carbon dioxide with a wet/dry adsorbent that has been used for the conventional gas separation processes.
Typical dry adsorbents for capturing carbon dioxide include a support (carrier), such as silica, mesoporous solid or carbon fibers, and an amine or polyamine absorbed physically thereto or bound chemically thereto, so that they may be applied to dry capturing processes using a fluidized bed reactor. Among the carriers for such adsorbents, a mesoporous solid allows production of adsorbent structures having a large surface area (in general, the capturing quality of an adsorbent depends on the surface area characteristics of a carrier as its support). However, such mesoporous solids require a large number of processes and times for their preparation, and thus mass production thereof is limited and commercial application thereof is not amenable. In addition, although the other structures, such as silica, are amenable to mass production, they have a relatively small surface area, and thus may provide low capturing efficiency when applied to a dry capturing process. Further, the adsorbents that have been suggested to date may not ensure structural strength sufficient to be applied to a fluidized bed process, and thus have a limitation in operating actual capturing processes.
Under these circumstances, there is a need for developing a carrier for an adsorbent and a method for preparing the same, wherein the carrier is a support for an adsorbent that directly affects the structural strength applicable to a fluidized bed process and the capturing quality of the adsorbent, the carrier and the method satisfying improvement of quality of the carrier and mass production thereof at the same time.